1. Technical Field of the Invention
The present invention relates generally to a bar code reading apparatus, and more particularly to an improved bar code reading apparatus which is operable to optically compress a bar code carrying information provided with a combination of lengths of bars of the code. This apparatus therefore allows the compressed bar code to be read completely in a one-time scanning operation.
2. Background Art
A postal bar code, as shown in FIG. 2, which is commonly employed in a U.S. post office network system is well known. This postal bar code 1 is designed to carry information formed with a combination of different lengths of a plurality of bars. The widths and spaces of the bars do not carry information at all.
For reading such a bar code, a bar code reader, as shown in FIG. 15, has been proposed in the art. This bar code reader includes a one-dimensional photoelectric converter 30 (i.g., a CCD linear image sensor) with an array of photosensitive elements being oriented parallel to the length of the bar of the code and an image-forming lens 2 operable to image the bar code on the photoelectric converter 30. When reading bar code Information, by carrying either an object such as mail on which the bar code is printed or sweeping the bar code reader in a width direction of the bar code, the photoelectric converter 30 receives light reflected from each bar to determine the length of the bar based on the degree of intensity of the reflected light.
Another bar code reader such as shown in FIG. 16 is also well known. This bar code reader includes a two-dimensional photoelectric converter 31 (i.g., a CCD area image sensor) which receives the entire bar code image to determine a combination of the lengths of the bars.
The above former prior art bar code reader, however, encounters a drawback in that in order to read the entire image of the bar code, it is necessary to move either the object disposing thereon the bar code or the photoelectric converter 30, resulting in an increased readout period of time.
Additionally, in the latter prior art bar code reader, although a time period required for reading the bar code completely is short, an expensive device such as the two-dimensional photoelectric converter 31 is necessary. Such a device increases the manufacturing costs of the whole system.